The invention relates to surgical apparatus and methods. More particularly, the invention relates to instruments and methods for use during knee replacement procedures.
Traditionally, when performing a partial knee replacement procedure, a practitioner first makes a horizontal femoral cut in the distal femur to remove diseased bone and provide a surface for receiving a femoral prosthesis. The proximal tibia is then cut to remove any diseased bone and provide a surface and sufficient clearance for receiving a tibial prosthesis. The femoral and tibial prostheses mate to form a replacement partial knee.
In this traditional procedure, the ultimate alignment of the leg after the prostheses are implanted is determined by the location of the tibial cut with respect to the femoral cut. After the femoral cut has been completed, the practitioner selects the location for the tibial cut based primarily on experience and with the understanding that tibial prostheses are available in a limited number of thicknesses. The tibial cut accordingly is made as close to the proximal end of the tibia as possible, based on how much of the tibia must be removed due to disease, plus whatever additional spacing is required to accommodate the closest standard sized tibial prosthesis. After the tibial cut is made, the prostheses are temporarily implanted and the alignment of the leg is analyzed. To adjust the leg alignment, the practitioner can replace the tibial prosthesis with one of a different thickness, can remove more bone, or can do both. This procedure is followed until the leg is in the desired alignment and balance.
Because the location of the tibial cut is independent of the location of the femoral cut, such a procedure may result in the practitioner making numerous cuts before the desired leg alignment and tension are attained. Also, as a result of this trial-and-error process, practitioners may at times remove more bone than necessary.
One method and instrumentation for making horizontal, femoral and tibial cuts is disclosed in U.S. Pat. Nos. 5,122,144 and 5,234,433, both to Bert et al. The Bert et al. patents disclose a first instrument for aligning and making the horizontal femoral cut, and a second instrument for aligning and making the horizontal tibial cut.
The present invention relates to instrumentation and methods for use during a knee replacement procedure. In one embodiment of the invention, the instrumentation includes first and second members configured to contact the distal femur and proximal tibia, respectively; an actuator linked to the first and second members; and a cutting guide. The first member is designed to contact either the medial or lateral side of the distal femur and to exert a force on the distal femur in a proximal direction. The second member is designed to contact the corresponding side of the proximal tibia, and to exert a force on the proximal tibia in a distal direction. The second member is movable with respect to the first member to allow a practitioner to rotate the tibia with respect to the femur in the horizontal plane. The actuator is controllable to move the second member, and to retain the second member in a desired position with respect to the first member. Accordingly, the actuator can be manipulated to rotate the tibia with respect to the femur (adjusting the tibiofemoral alignment), and to retain the leg in the desired alignment. The cutting guide is designed to be temporarily fixed to the proximal tibia and the distal femur. The cutting guide has openings therethrough that are sized and shaped to guide a surgical saw for making the horizontal, tibial and femoral cuts.
The system of this embodiment allows the practitioner to position the leg in the alignment that is desired at the end of the implant procedure, and to cut both the femur and the tibia while the leg is fixed in this alignment so that preselected prostheses can be implanted in the knee and the knee will have the desired alignment after the prostheses have been implanted. The distal femoral and proximal tibial cuts can be parallel to each other and perpendicular to the tibial weight-bearing axis. The system may also allow the practitioner to perform the procedure using a smaller incision than that traditionally used, and to avoid excessive bone removal.
In another embodiment of the present invention, the instrumentation has a spacer used in place of the first and second members discussed above. In this particular embodiment, the practitioner has a number of potential spacers available for use, each spacer having a distal end with a distinct thickness. The practitioner can select the desired spacer that creates the preferred leg alignment, then can make the femoral and tibial cuts as described above. As with the previous embodiment, this embodiment allows the practitioner to set the ultimate alignment of the leg prior to making the bone cuts, and to create parallel cuts which are perpendicular to the floor and which avoid excessive bone removal.
In another embodiment, the instrumentation of the present invention incorporates a cutting and drilling guide for use in preparing the distal femur to receive a femoral prosthesis. The cutting and drilling guide has a bottom surface that is shaped to conform with the distal femur after the horizontal femoral cut has been made. The guide has a posterior portion that engages the posterior distal femur, and an anterior portion that mates with the anterior distal femur. The proximal portion is contoured to closely conform with the posterior distal femur to allow the practitioner to flex the leg during the procedure to confirm the guide""s alignment. The anterior portion of the guide has a laterally tapered thickness that complements the patella. The guide accordingly can be used without the practitioner first dislocating the patella.
Embodiments of the present invention are also directed to methods for aligning the leg prior to performing knee surgery, methods for aligning the horizontal femoral and tibial cuts, and methods for making both the horizontal tibial and the horizontal femoral cuts using a single guide to create the parallel cuts and the desired, ultimate alignment in the leg. The present invention is also directed toward various combinations of the above instrumentation and methods, as well as the instrumentation and methods used in connection with other such instruments and used in performing other such methods.